Originally Posted by
msmorley
I don't think it's a stupid question at all: I would have thought that the traces found around London could be explained by the victim excreting traces of his "dose" but not those on the aircraft. Unless the would-be "assassin" was already poisoned himself, I wonder what is being seen here...
Assuming specific evidence of Polonium 210 was found, and not just any old radio-nuclide, what is being seen here is almost surely background stuff. For example, Polonium 210 is present in lead solder, so prospectively, electronic circuitry aboard an aircraft could emit alpha particles from Polonium 210. [Assuming the alpha particles could freely reach the scanning device.]
Almost suredly, the assassin did not poison himself or herself and thus none of his or her bodily secretions (sweat, mucus, saliva) would contaminate an aircraft with the poison.
This whole issue of the planes strikes me as an investigative tangent gone amuck, and will ultimately prove to be non-productive other than for journos in search of big headlines.